Apparatus and method for cleaning and sealing of bottom pour crucible

ABSTRACT

Cleaning and sealing of a bottom pour crucible in a casting chamber is accomplished by a rotary arc wheel mounted in the casting chamber for movement essentially laterally across the bottom opening of the crucible to clean the drool or metal projections extending from the opening. The wheel can be movable toward and away from the opening so that it can alternately close and open the same. In the alternative, a shiftable gate can be moved into and out of closing relationship to the opening after the drool has been removed. One form of the wheel comprises a spherical electrode. Another embodiment of the wheel comprises a metallic disk rotatable about a central axis. This invention relates to improvements in the melting of materials in arc furnaces and, more particularly, to a method and apparatus for removing the drool from the bottom orifice of bottom pour crucibles.

United States Patent no Schlienger i l APPARATUS AND \1 ETHUD FUR CLEANING AND SEALING ()F BOTTOM POUR CRUCIBLE Max P. Schlienger, San Rafael.

Calif.

[75] Inventor:

|73| Assignee: Schlienger. Inc., San Rafael. Calif.

l22| Filed: Nov. 25, I974 [2|] Appl. No: 526.658

[ 5! Dec. 2, I975 Primary Examiner-Rt N. Envall. Jr. Attorney. Agent, or FirmTownsend and Townsend {57] ABSTRACT Cleaning and sealing of a bottom pour crucible in a casting chamber is accomplished by a rotary arc wheel mounted in the casting chamber for movement essentially laterally across the bottom opening of the eruci ble to clean the drool or metal projections extending from the opening. The wheel can be movable toward and away from the opening so that it can alternately close and open the same. In the alternative. a shiftahle gate can be moved into and out ofclosing relationship to the opening after the drool has been removed. One form of the wheel comprises a spherical electrode. Another embodiment of the wheel comprises a metallit: disk rotatable about a central axis.

This invention relates to improvements in the melting of materials in are furnaces and. more particularly. to a method and apparatus for removing the drool from the bottom orifice of bottom pour crucibles.

15 Claims, 4 Drawing Figures 4s COOLANT now U.S. Patent Dec. 2, 1975 APPARATUS AND METHOD FOR CLEANING AND SEALING OF BOTTOM POUR CRUCIBLE BACKGROUND OF THE INVENTION Many attempts have been made to enable the successful bottom tapping of crucibles especially as related to skull melting or semi-skull melting. In this context, semi-skull melting refers to the melting of materials in a crucible with a partially water-cooled metal surface and a partially refractory lining to enable both grounding of the melt to the crucible and also to allow for the conservation of maximum heat energy.

One of the major problems relating to bottom pour crucibles is the formation of drool or solid metal projections hanging from the lower water-cooled, metallic tapping spout of the crucible. This problem prevents the resealing of the tapping spout when the melting operation is to be interrupted and then restarted at another time.

SUMMARY OF THE INVENTION The present invention is directed to a solution of the foregoing problem by providing apparatus and a method for cleaning the drool from the bottom opening of the tapping spount of a bottom pour crucible and then to close the opening as as to place the crucible in a condition awaiting a subsequent melting operation.

The apparatus of the present invention utilizes a rotary arc electrode in the casting chamber containing the bottom pour crucible. The electrode can have any one of a number of different shapes and can be of any desired size so that it can be accommodated to the shape and size of the tapping orifice at the bottom of the crucible. For instance, the electrode can be spherical in shape or can assume the shape of a wheel or disk. Also, it can be water-cooled to prevent structural damage thereto when an arc is established between the electrode and the crucible for cleaning the tapping orifice.

The electrode can be mounted so that, after the drool has been removed, the electrode itself can be moved into a position closing the bottom opening of the crucible. In the alternative, other structure, such as a shiftable gate which is either water-cooled or of a refractory material, can be positioned adjacent to the bottom of the crucible for movement into and out of closing relationship to the opening of the tapping spout thereof.

The primary object of this invention is to provide apparatus and a method for cleaning the drool from the bottom opening ofa bottom pour crucible by establishing an electric are between the crucible and a rotary arc electrode so that the drool is melted off by the arc and the opening can be immediately closed thereafter to place the crucible in condition awaiting the next melting operation.

Another object of this invention is to provide apparatus and a method of the type described wherein the electrode can be of any size and shape depending upon the size and shape of the tapping spout of the crucible and can also be used to close the opening in the tapping spout in lieu of additional structure, such as a shiftable gate, to thereby simplify the cleaning and closing of the opening while control of the arc can be had at all times.

Other objects of this invention will become apparent as the following specification progresses, reference being had to the accompanying drawing for an illustration of several embodiments of the apparatus. In the drawings:

FIG. 1 is a vertical section through an arc furnace having a bottom pour crucible and provided with a rotary arc wheel for cleaning and closing the bottom tap thereof, certain portions being shown schematically;

FIG. 2 is a view similar to FIG. I but showing a different position of the rotary arc wheel with respect to the bottom of the crucible;

FIG. 3 is a view similar to FIG. 2 but showing the closing of the bottom tap by the rotary arc wheel; and

FIG. 4 is a view similar to FIG. I but illustrating another embodiment of the rotary arc wheel for cleaning and closing the bottom tap of a bottom pour crucible.

A first embodiment of the arc furnace of this invention is broadly denoted by the numeral and is shown in FIGS. 1-3. Apparatus 10 includes a bottom pour crucible 12 whose walls have fluid passages therein for receiving a fluid coolant. The crucible is in a stationary position in a casting chamber 14 above and spaced from the open top of a receptacle 16 which receives molten material from the crucible when the molten material gravitates from the crucible through the tapping orifice 18. The material in crucible I2 is melted in any suitable manner, such as by an electric are established between the upper surface 20 of the material 22 in the crucible and a rotary arc wheel 24 mounted on a shaft 26 extending upwardly and away from surface 20. The are is established when a potential different exists between material 22 and wheel 24. Because of the drool or metal projections 28 hanging from spout 18, the latter cannot be properly closed or rescaled after a melting operation. The present invention eliminates this problem by utilizing a rotary arc wheel 30 in the form of a spherical electrode 32 mounted on a shaft 34 extending through sidewall 36 of casting chamber 14 and coupled with a bearing 38 allowing it to rotate about its longitudinal axis as denoted by arrow 40. Shaft 34 is also coupled with a translating mechanism 42 which allows shaft 34 to reciprocate in the direction of arrows 44. Moreover, shaft 34 is coupled with a pivoting mechanism 46 which allows shaft 34 to be reciprocated in the direction of arrows 48 about a horizontal axis through point 50 which is surrounded by a ball-type vacuum seal 52 coupling shaft 34 to sidewall 36. Thus, electrode 32 can not only move horizontally back and forth beneath tapping spout 18 but it can rotate about an axis through shaft 34 and can pivot upwardly and downwardly so that it can alternately close and open tapping spout I8.

A power supply 54 is coupled by a lead 56 to shaft 34 and by a lead 58 to ground potential. Similarly, a lead 60 couples crucible I2 to ground potential. Control means 62 controls the voltage and current of power supply 54 so that an electric arc can be established between electrode 32 and tapping spout 18 to melt projections 28 progressively to clean the bottom opening of spout l8 and to permit rescaling of the same. FIG. 2 illustrates electric are 64 as it cleans and removes projections 28. FIG. 3 shows electrode 32 in a position closing the lower opening of tapping spout 18 so as to reseal the bottom of crucilbe l2. Immediately before the electrode moves into the position of FIG. 3, rotation of the electrode is stopped, then it is seated into the bottom opening of tapping spout I8.

In operation. electrode 32 is normally located at the side as shown in FIG. 1 during the final stages of melting of material 22 and the gravitation of the material into receptacle I6. When the tapping of melting material 22 is accomplished. projections 28 form and prevent the closing of the bottom opening of tapping orifice 18. Then, electrode 32 is moved into proximity to but spaced from spout I8 and an electric arc is established between the electrode and the bottom of the crucible. The electrode is rotated about its longitudinal axis and progressively and slowly moves across the bottom opening of tapping spout 18 in the manner shown in FIG. 2 to remove projections 28 by a melting process. Eventually, these projections will be completely removed and the electrode is then elevated by operation of pivot mechanism 46. Eventually, the rotation of the electrode is stopped and then it is further elevated into the position of FIG. 3, closing the bottom opening of the crucible and resealing it.

When it is desired to commence melting of material, electrode 32 may or may not be lowered and withdrawn to the position of FIG. 1 depending upon the size and physical characteristics of the charge material. Tapping of crucible I2 is effected by removing the chill effect of electrode 32 and applying superheat to melt material 22 by means of arc wheel 24 until the solidified material in orifice 18 becomes liquidus and tapping commences. If desired, heat can be applied from the bottom of the crucible to facilitate faster tapping after removal of electrode 32.

It is to be noted that electrode 32 is continuously cooled during its use in cleaning and rescaling the bottom opening of the crucible 12. To this end, shaft 34 can be tubular to allow passage therethrough of a fluid coolant in opposed directions. Electrode 32 itself can be provided with a fluid passage therethrough communicating with the passages in shaft 34 to receive the coolant and allowing cooling of the electrode. Thus, the shaft is coupled to a suitable source of coolant (not shown) which continuously supplies the fluid coolant to the electrode.

Another embodiment of the apparatus is shown in FIG. 4 and is essentially the same in construction as that shown in FIG. 1 except that, instead of a spherical electrode, the electrode comprises a wheel 70 mounted for rotation in a generally horizontal plane by a shaft 72 coupled to a bearing 74 externally of casting chamber 14. Thus, wheel 70 rotates in the direction of circular arrow 76. A pivoting mechanism 78 permits pivotal movement of wheel 70 about a horizontal axis 80 through a ball-type vacuum seal 82 in the top 84 of casting chamber 14. Thus, arc wheel 70 can move essentially horizontally across the bottom opening of tapping spout 18 to clean the projections 28 therefrom.

Shaft 72 is also coupled to a translation mechanism 84 which allows arc wheel 70 to be raised and lowered. When it is raised, it can plug or close the bottom opening of tapping orifice I8. Moreover, the rotary arc wheel can be provided with passage means therethrough communicating with passage means in shaft 72 for receiving a coolant so that the wheel can be continuously cooled as an arc is established between it and tapping spout 18.

It is not necessary that the electrode of FIG. 1 or the electrode of FIG. 4 be used for plugging or closing the bottom opening of crucib e 12. To this end, another structure could be used for this purpose, such as a water-cooled, shiftable gate 90 mounted in any suitable manner for reciprocation in the direction of arrow 92 adjacent to the bottom opening of tapping spout 18. A fluid piston and cylinder assembly 94 can be provided for causing the reciprocation of the gate. Coolant can flow to gate by way of tubes or other conduits either through or bypassing assembly 94. In the alternative, gate 90 need not be watercooled but could be of graphite or of a refractory material.

Other shapes of electrodes could be utilized to accomplish the foregoing purpose, depending upon the particular shape of the bottom hole of tapping orifice 18. For instance, the electrode may be of tapered or cylindrical design so long as the cleaning action can be realized by the controlled are between the electrode and the crucible. Such equipment can be used for a variety of melting applications where conductive material is being melted and where a proper ground or electrical interface can be attained with the material in the tapping orifice. Moreover, the angles at which the elec trodes approach the tapping orifice can be different from those shown in FIGS. 1 and 4.

I claim:

1. Apparatus for cleaning the opening at the bottom ofa bottom pour crucible comprising: a rotary arc electrode; means coupled with the electrode for mounting the same for rotation and for movement along a path across and adjacent to said opening of the crucible; means coupled with said electrode for rotating the same and for moving it along said path; and means coupled with said electrode and adapted to be coupled with said crucible for establishing an electric are there between, whereby the heat from the arc will clean the opening as the electrode rotates and moves along said path.

2. Apparatus as set forth in claim 1, wherein is included means coupled with said electrode for moving the same toward and into closing relationship to said opening, whereby the opening can be closed by the electrode after the opening has been cleaned.

3. Apparatus as set forth in claim 1, wherein is included gate means independent of said electrode and mounted for movement relative to the crucible for closing said opening after the latter has been cleaned.

4. Apparatus as set forth in claim 1, wherein the electrode has means for receiving a fluid coolant.

5. Apparatus as set forth in claim I, wherein said electrode is spherical, said mounting means including a shaft secured to and extending outwardly from the electrode.

6. Apparatus as set forth in claim 1, wherein said electrode comprises a wheel having a central axis, said mounting means including a shaft secured to the wheel and extending therefrom in a direction coincident with said central axis.

7. In combination: means defining a casting chamber having a wall; a crucible having a bottom opening and positioned in said casting chamber; an electrode in the casting chamber; a shaft coupled with the electrode and extending through the wall; means mounting the shaft for rotation about its longitudinal axis; means coupled with the shaft for mounting the same for move ment in a manner permitting the electrode to move along a path spaced below and extending across said bottom opening; electrical power means coupled with said electrode and said crucible for establishing an electric arc therebetwecn. whereby the heat of the arc will clean the opening as the electrode rotates and moves along said path; and means in said shaft and said electrode for receiving a fluid coolant.

8. The combination of claim 7, wherein is included means coupled with said shaft for moving said electrode along a second path into closing relationship to said bottom opening.

9. The combination of claim 7, wherein is included a gate, means mounting said gate in said casting chamber for movement into and out of closing relationship to said bottom opening, and means coupled to said gate for moving the same, whereby the gate can be used to close said bottom opening after the latter had been cleaned 10. The combination of claim 7, wherein is provided a seal mounting the shaft on the wall of said chamber.

H. A method for cleaning the drool from the bottom opening of a bottom pour crucible comprising: establishing an electric arc near said bottom opening; moving said are across said opening to melt the drool therefrom and thereby clean the opening; and closing the opening after the same has been cleaned.

12. A method as set forth in claim 11, wherein said establishing step includes placing an electrode near said bottom opening. and creating and maintaining said are between said electrode and said crucible, said moving step including shifting the electrode along a predetermined path.

13. A method as set forth in claim 12, wherein said closing step includes moving the electrode into closing relationship to said bottom opening.

14. A method as set forth in claim 12, wherein is included the steps of rotating said electrode and cooling the same as the electrode is shifted along said path and as said are is maintained.

15. A method as set forth in claim 11, wherein is included the steps of confining the crucible within a confined space, and controlling said establishing, moving and closing steps from a location externally of said space. 

1. Apparatus for cleaning the opening at the bottom of a bottom pour crucible comprising: a rotary arc electrode; means coupled with the electrode for mounting the same for rotation and for movement along a path across and adjacent to said opening of the crucible; means coupled with said electrode for rotating the same and for moving it along said path; and means coupled with said electrode and adapted to be coupled with said crucible for establishing an electric arc therebetween, whereby the heat from the arc will clean the opening as the electrode rotates and moves along said path.
 2. Apparatus as set forth in claim 1, wherein is included means coupled with said electrode for moving the same toward and into closing relationship to said opening, whereby the opening can be closed by the electrode after the opening has been cleaned.
 3. Apparatus as set forth in claim 1, wherein is included gate means independent of said electrode and mounted for movement relative to the crucible for closing said opening after the latter has been cleaned.
 4. Apparatus as set forth in claim 1, wherein the electrode has means for receiving a fluid coolant.
 5. Apparatus as set forth in claim 1, wherein said electrode is spherical, said mounting means including a shaft secured to and extending outwardly from the electrode.
 6. Apparatus as set forth in claim 1, wherein said electrode comprises a wheel having a central axis, said mounting means including a shaft secured to the wheel and extending therefrom in a direction coincident with said central axis.
 7. In combination: means defining a casting chamber having a wall; a crucible having a bottom opening and positioned in said casting chamber; an electrode in the casting chamber; a shaft coupled with the electrode and extending through the wall; means mounting the shaft for rotation about its longitudinal axis; means coupled with the shaft for mounting the same for movement in a manner permitting the electrode to move along a path spaced below and extending across said bottom opening; electrical power means coupled with said electrode and said crucible for establishing an electric arc therebetween, whereby the heat of the arc will clean the opening as the electrode rotates and moves along said path; and means in said shaft and said electrode for receiving a fluid coolant.
 8. The combination of claim 7, wherein is included means coupled with said shaft for moving said electrode along a second path into closing relationship to said bottom opening.
 9. The combination of claim 7, wherein is included a gate, means mounting said gate in said casting chamber for movement into and out of closing relationship to said bottom opening, and means coupled to said gate for moving the same, whereby the gate can be used to close said bottom opening after the latter had been cleaned.
 10. The combination of claim 7, wherein is provided a seal mounting the shaft on the wall of said chamber.
 11. A method for cleaning the drool from the bottom opening of a bottom pour crucible comprising: establishing an electric arc near said bottom opening; moving said arc across said opening to melt the drool therefrom and thereby clean the opening; and closing the opening after the same has been cleaned.
 12. A method as set forth in claim 11, wherein said establishing step includes placing an electrode near said bottom opening, and creating and maintaining said arc between said electrode and said crucible, said moving step including shifting the electrode along a predetermined path.
 13. A method as set forth in claim 12, wherein said closing step includes moving the electrode into closing relationship to said bottom opening.
 14. A method as set forth in claim 12, wherein is included the steps of rotating said electrode and cooling the same as the electrode is shifted along said path and as said arc is maintained.
 15. A method as set forth in claim 11, wherein is included the steps of confining the crucible within a confined space, and controlling said establishing, moving and closing steps from a location externally of said space. 